Full Product Manual

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Formulas for Xerigation Design Page 77
FORMULAS FOR
XERIGATION DESIGN
K
c
is an adjustment factor to PET that accounts for the needs of a specific plant in
specific growing conditions. It is also known as the “crop coefficient” or the “plant
factor.”
The formula for K
c
is:
K
c
= Species Factor x Density Factor x Microclimate Factor
The water requirement for a densely planted hydrozone is measured in inches
per day.
The formula for the water requirement of a densely planted area is:
Water Requirement (inches per day) = K
c
x PET
Where:
K
c
= Crop coefficient (plant factor) of the base plant
PET = Published daily evapotranspiration rate (inches per day)
In order to determine the water requirement of individual plants you must first
calculate the area of the plant’s canopy.
The formula for the area of a plant’s canopy is:
Area (square feet) = 0.7854 x Diameter (feet) x Diameter (feet)
A
Water Require-
ment For a Dense
Planting Scheme
Plant Canopy
Area
®